Composite guidewire

ABSTRACT

The composite guidewire includes an elongated, flexible core formed from a nickel titanium alloy, with a distal tapered portion, a reinforcement tube disposed over the proximal region of the core, a primary coil disposed over the tapered distal region of the core, and a coating of a heat shrinkable material. A distal tip is secured to the distal end of the core. The proximal reinforcement member has a distal tapered portion, to provide for a transition in stiffness of the guidewire. The heat shrinkable coating is formed from an elongated tube of PTFE, and the distal primary coil is formed from one or more nickel titanium alloy strands or wires, one or more platinum wires, or a combination. The distal tip may be formed of platinum or a tantalum filled epoxy.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to vascular interventionalmedical devices, and more particularly concerns guide wires for use in atherapeutic system or for delivery of medical devices.

[0003] 2. Description of Related Art

[0004] Conventional minimally invasive catheter based therapiestypically require guidewires that are one to two meters long extendingthrough a longitudinal lumen in the catheter, and that are torqueableand pushable at the proximal end, yet soft and flexible at the distalend. Many such guidewires are made of stainless steel or the like, andare ground to tapers which provide the desired bending properties alongthe guidewire. It is useful for such guidewires to be torqueable fromthe base of the guidewire for manipulation of the distal tip, which istypically bent, for guiding the distal tip through vascular passages.While such guidewires need to be torqueable, pushable and resilient,particularly at the proximal regions of the guidewire, they also need tobe flexible, particularly at the distal regions of the guidewire.

[0005] One prior guidewire for use with a catheter includes a core wireformed from a nickel titanium alloy, with a tapered distal tip portionand a distal end cap, covered by a sheath of material such aspolyurethane, polyethylene, nylon, silicone, polytetrafluoroethylene,cellulose, starch or gelatin. Another prior guidewire comprises acomposite guidewire with a core of stainless steel or a nickel titaniumalloy, a tapered distal region ending in a distal flexible coil and endcap, also having a major portion of the guidewire covered by a thinlayer of polymeric material, such as polysulfones, polyfluorocarbons,polyolefins, polyesters, polyamides, polyurethanes, blends andcopolymers such as polyether block amides.

[0006] However, there remains a need for a guidewire with enhancedproximal stiffness, with a stiff, high modulus reinforcement, allowingfor greater manipulation of the guidewire by the physician, along withgreater distal tip flexibility with radiopacity. The present inventionmeets these needs.

SUMMARY OF THE INVENTION

[0007] Briefly, and in general terms, the present invention provides animproved composite guidewire with a proximal high modulus reinforcementmember for promoting greater proximal stiffness, with a tapered distalregion and distal radiopaque coil providing greater distal tipflexibility with radiopacity. The composite structure thusadvantageously provides for a composite guidewire with greaterresilience, a transition in stiffness, and tip flexibility. The proximalstiffer, high modulus member, covering or reinforcing a nickel alloycore, can be formed of high modulus metals such as stainless steel,titanium, and the like, allowing for greater manipulation of theguidewire by the physician, while the distal coil has enhanceddurability, being formed from a composite strand of a nickel titaniumalloy and platinum.

[0008] The present invention accordingly provides for a compositeguidewire having an elongated, flexible core formed from a nickeltitanium alloy having proximal and distal regions, with the distalregion having a tapered portion, a reinforcement tube disposed over theproximal region of the core, a primary coil disposed over the tapereddistal region of the core, with a coating of a heat shrinkable materialdisposed over at least a portion of the reinforcement member, anintermediate portion of the core, and at least a portion of the primarycoil, and a distal tip secured to the distal end of the core.

[0009] In a presently preferred embodiment, the core is a nickeltitanium alloy rod, although the core may alternatively be formed of oneor more elongated strands of nickel titanium alloy, or an elongatedtube. In another presently preferred aspect, the proximal reinforcementmember is formed as an elongated ground stainless steel hypo tube,although the reinforcement member may alternatively be formed of anelongated tube made of titanium, or a nickel titanium alloy. In anotherpresently preferred aspect, the proximal reinforcement member is formedwith a distal tapered portion, to provide for a transition in stiffnessof the guidewire. In a presently preferred embodiment, the heatshrinkable coating is formed from an elongated tube ofpolytetrafluoroethylene (PTFE), although the heat shrinkable coating mayalso be selected from other heat shrinkable materials such aspolyethylene, for example. In another presently preferred aspect of theinvention, the distal primary coil is formed from one or more nickeltitanium alloy strands or wires, and in another presently preferredaspect the distal primary coil is formed from one or more platinumwires, or a combination of one or more nickel titanium alloy strands andone or more platinum wires. In one currently preferred embodiment, thedistal tip is formed of platinum, and is bonded to the distal end of thecore such as by welding, or soldering, or the like, although the distaltip may also be formed of other materials such as a tantalum filledepoxy adhesively bonded to the distal end of the core.

[0010] These and other aspects and advantages of the invention willbecome apparent from the following detailed description and theaccompanying drawings, which illustrate by way of example the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a longitudinal sectional schematic diagram of thecomposite guidewire of the invention;

[0012]FIG. 2 is a transverse sectional view taken along line 2-2 of FIG.1;

[0013]FIG. 3 is a transverse sectional view similar to FIG. 2illustrating a first alternate preferred embodiment;

[0014]FIG. 4 is a transverse sectional view similar to FIG. 2illustrating a second alternate preferred embodiment;

[0015]FIG. 5 is a transverse sectional view taken along line 5-5 of FIG.1;

[0016]FIG. 6 is a transverse sectional view taken along line 6-6 of FIG.1;

[0017]FIG. 7 is a transverse sectional view taken along line 7-7 of FIG.1;

[0018]FIG. 8 is a transverse sectional view taken along line 8-8 of FIG.1;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Guidewires used for vascular therapeutic intervention typicallyneed to be torqueable, pushable and resilient over a proximal region ofthe guidewire, and flexible, over the distal region of the guidewire.While tapered guidewires can provide a range of proximal stiffness andtorqueability to distal flexibility, enhancement of the proximalstiffness of such guidewires can give a physician manipulating theguidewire better control over the distal positioning of the guidewire.

[0020] As is illustrated in the drawings, the invention is embodied in acomposite guidewire 10 illustrated in FIG. 1, having a centralelongated, flexible core 12 preferably formed from a nickel titaniumalloy such as Nitinol, having a proximal region 14 and a distal region16. The distal region of the core preferably includes a tapered portion18, to provide for a gradual transition to increased flexibility in thedistal region of the guidewire. The core is preferably formed as anelongated rod, as illustrated in FIG. 2, although the core may also beformed of a one or more strands 20 of a nickel titanium alloy such asNitinol as shown in FIG. 3. The one or more strands may be helicallywound, or may run longitudinally parallel along the length of theguidewire. Alternatively, the core may also be formed from an elongatedtube 22 such as a hypo tube made of a nickel titanium alloy such asNitinol, as shown in FIG. 4.

[0021] A proximal reinforcement tube 24 is preferably disposed over theproximal region of the core, with the reinforcement tube preferablyhaving a tapered distal portion 26, to provide for a transition instiffness of the guidewire. The proximal reinforcement member iscurrently preferably formed from an elongated ground stainless steelhypo tube, although the reinforcement member may alternatively be formedof an elongated tube made of titanium, or a nickel titanium alloy suchas Nitinol.

[0022] A primary coil 28 is preferably bonded over the tapered distalregion of the core, such as by welding, solder, or by adhesive such ascyanoacrylate. The primary coil is currently preferably formed from oneor more nickel titanium alloy strands or wires as described above, oneor more platinum wires to provide radiopacity to the primary coil, or acombination of one or more nickel titanium alloy strands and one or moreplatinum wires. A distal tip 30 is preferably secured to the distal end32 of the core and to the distal end 32 of the primary coil. In onecurrently preferred embodiment, the distal tip is formed of platinum,and is bonded to the distal end of the core such as by welding, orsoldering, or the like, although the distal tip may also be formed ofother materials such as a tantalum filled epoxy adhesively bonded to thedistal end of the core and to the distal end of the primary coil.

[0023] An outer coating of a heat shrinkable polymeric material 34, suchas an elongated tube of polytetrafluoroethylene (PTFE), is alsopreferably disposed over at least a distal portion of the reinforcementmember 36, an intermediate portion 38 of the core, and at least aportion 40 of the distal primary coil. The heat shrinkable coating mayalso be selected from other similar suitable heat shrinkable materialssuch as polyethylene, for example.

[0024] It will be apparent from the foregoing that while particularforms of the invention have been illustrated and described, variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

What is claimed is:
 1. A composite guidewire, comprising: an elongated,flexible core formed from a nickel titanium alloy, said core havingproximal and distal regions, with said distal region having a taperedportion; a reinforcement tube disposed over said proximal region of saidcore; a primary coil disposed over said tapered distal region of saidcore; coating of a heat shrinkable material disposed over at least aportion of said reinforcement member, an intermediate portion of saidcore, and at least a portion of said primary coil; and a distal tipsecured to the distal end of said core.
 2. The composite guidewire ofclaim 1, wherein said elongated, flexible core comprises a rod.
 3. Thecomposite guidewire of claim 1, wherein said elongated, flexible corecomprises at least one strand.
 4. The composite guidewire of claim 1,wherein said elongated, flexible core comprises a hypo tube.
 5. Thecomposite guidewire of claim 1, wherein said reinforcement tubecomprises an elongated ground stainless steel hypo tube.
 6. Thecomposite guidewire of claim 1, wherein said reinforcement tubecomprises titanium.
 7. The composite guidewire of claim 1, wherein saidreinforcement tube comprises a nickel titanium alloy.
 8. The compositeguidewire of claim 1, wherein said reinforcement tube comprises a distaltapered portion.
 9. The composite guidewire of claim 1, wherein saidcoating of a heat shrinkable material comprises an elongated tube ofpolytetrafluoroethylene.
 10. The composite guidewire of claim 1, whereinsaid primary coil comprises at least one nickel titanium alloy strand.11. The composite guidewire of claim 1, wherein said primary coilcomprises at least one platinum wire.
 12. The composite guidewire ofclaim 10, wherein said primary coil further comprises at least oneplatinum wire.
 13. The composite guidewire of claim 1, wherein saiddistal tip comprises platinum.
 14. The composite guidewire of claim 1,wherein said distal tip comprises tantalum filled epoxy.